Many devices or objects used in daily life are operated nowadays by input devices, such as electric switches, control levers, touch-sensitive screens (touchscreen), slide controls, keyboards and the like, in which the input occurs in the form of feedback via other sensory organs. If, for example, a cursor is to be controlled on a screen using a so-called mouse, the input occurs as a result of manual manipulation of the mouse, while the feedback occurs visually as a result of viewing the screen. When changing the volume on a radio, in many devices nowadays it is only a matter of holding a button down, whereby the length of time the button is pressed determines the degree of change in volume In this case, the feedback is acoustic.
In the case of a tactile input, it is desirable to receive a direct, haptic feedback wherein the tactile input (force, path, direction) is experienced directly as a tactile experience and not later via a potentially time-delayed system, such as for example, by way of a signal not directly connected to the input.
For this purpose magnetically positioned input elements are suitable.
U.S. Pat. No. 7,898,523 B1 discloses an input device consisting of two housings, each of which are closed, and which have surfaces in contact with one another and are held in contact by magnets. Arranged in one housing is a circuit board and an optical sensor which scans the contact surface of the other housing and generates an output signal that indicates the relative position of both housings relative to one another.
U.S. Pat. No. 6,762,748 B2 discloses a magnetic input device that includes a housing, the wall of which has an opening in which a displaceable magnet is mounted. The relative position of this magnet is detected by magnetic flux sensors.
U.S. Pat. No. 6,509,888 B1 discloses an input device with movable magnets and sensors in the form of coils. Displacement of the magnet induces a voltage in the coil which is evaluated.
DE 199 62 789 A1 discloses an actuation assembly for a window pane for a motor vehicle that includes a housing with an opening therein through which an actuating element protrudes, the element being coupled to a slide member that carries contact tabs which touch the contacts on a fixed circuit board.
EP 1 223 541 B1 describes an input device in the form of a remote control in which, for controlling a cursor on a display screen, a movable sliding part with a first magnet attached thereto is moved relative to a second fixed magnet, the resulting magnetic field being measured by Hall-sensors, from which the position of the movable sliding part can be determined. As a result of the interaction of both magnets the slidable part is moved to a predetermined position in the absence of an external force. Only through external force, for example, with the finger of an operator, is it possible to move the slidable part out of its idle position, wherein the force required for displacement is a function of the position of the magnets relative to one another, such that the user receives a tactile or perceptibly haptic feedback.
A third fixed magnet may also be provided, so that the slidable part can be moved between two idle positions. The displacement from both idle positions requires in each case an external force.
Further examples of input devices with magnets are known from the following documents:                DE 10117956 B4, DE 102005018275 A1,        DE 102007002189 A1, DE 202005019271 U1,        EP 0810544 A2, EP 1901005 A2,        JP 06318134 A, JP 2005004365 A,        U.S. Pat. No. 5,504,502 A, U.S. Pat. No. 7,187,360 B2,        U.S. Pat. No. 7,489,296 B2, US 2002/0054012 A1,        US 2002/0125977 A1, US 2004/0252104 A1,        US 2005/0068134 A1, US 2006/0209019 A1,        WO 03/054782 A1, WO 2006/130723 A2,        WO 2006/131520 A1 and WO 2008/016386 A2.        
Most of the aforementioned documents use Hall sensors, which measure the magnetic flux density from which a signal for the position of the movable magnets can be derived.
In WO 00/70438 it is noted that Hall sensors are relatively expensive and are only capable of measuring the magnetic flux density, so that at least two Hall sensors are required for detecting the direction of movement of a magnet. Hence, this document proposes using sensors in the form of coils. When a magnet is moved relative to a coil, an electric voltage or current potential is induced in said coil, wherein a voltage pulse enables the direction of movement to be detected as well because the voltage pulse starts with a rising or falling edge depending on the direction of movement. The drawback of this device, however, is that it can detect only a movement but no static condition.
U.S. Pat. No. 5,698,976 A describes an input device having a plate made of a magnetic material, the surface of which, however, has regular geometric configurations but which differ in the X- and Y-direction in the form of depressions and peaks. A magnet is displaceable relative to this plate and a sensor in the form of a coil is moved in concert with said magnet. The magnetic flux varies as a result of the differing surface geometry of the plate, which variation is detected by the coil.
In the older, non-published German patent application DE 10 2010 012 247 an input device is described in which a magnetic operating part is displaceable in a sliding block guide along a housing wall. The relative position of the magnetic part is detected by sensors which comprise a coil that forms a frequency-determining component of an oscillator. A change in the position of the magnetic part alters the inductance value of the coil and with that the frequency of the oscillator.
In the older, non-published German patent application DE 10 2010 019 596, an input device is described in which a movable magnetic part is arranged along a circular path. Here, too, the magnetic part is displaceable relative to the housing wall to which it is pivotally attached. A sensor for the position of the movable magnetic part is provided also in the form of coils with an oscillator.
The problem with these devices is the attachment and operation of the movable magnetic parts on the housing wall. If the magnetic part is held in place solely by magnetic force, it can be removed and become lost. If it is attached to the housing wall by means of a sliding block guide or a swivel, the design itself is mechanically complex.